[cs13001] Lab 12

[Mikhail Nesterenko]

> I am receiving an error in the remove portion of my code in Lab 12 that says
> "vector iterator not incrementable"
> 
> else if (ans == 'r') {
>    cin >> num;
>    vector<int>::iterator toRemove = v.begin();
>    for (vector<int>::iterator ip = toRemove; ip != v.end(); ++ip)
>     if (num == *ip) {
>      toRemove = ip;
>      v.erase(toRemove);
>     }
>   }
> 

After using erase() all iterators pointing to the vector on which the
erase was carried out including, in your case, ip, are
_invalidated_. Meaning that you cannot refer to them or increment
them, as you do in the for-loop. This is because erase() may force
to re-allocate vector's internal structure holding the data.

So, afer erase(), you need to either break out of the loop (easiest for
this lab), or re-initialize all the iterators. This re-initialization
is often done using the proprety of erase() that returns an iterator
to the element following the erased element. Here is an example:

   for(auto it=vect.begin(); it != vect.end();)
      if (/* need to erase */)
         it = vect.erase(it);
      else
         ++it;

Thanks,
--
Mikhail